$ git clone -n https://src.fedoraproject.org/rpms/xstream.git /var/lib/mock/f40-build-2441041-60990/root/chroot_tmpdir/scmroot/xstream
Cloning into '/var/lib/mock/f40-build-2441041-60990/root/chroot_tmpdir/scmroot/xstream'...
$ git fetch origin a9a83044fa0bb9c8e87f2a06e51fbdef7aca1ca0:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/xstream
 * [new ref]         a9a83044fa0bb9c8e87f2a06e51fbdef7aca1ca0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at a9a8304 Remove trailing whitespace